Britain’s leading supermarkets have launched an investigation into claims of bad practice by a key UK fishing group after the Financial Times exposed the mistreatment of migrant crew on several of its member boats.

The probe into the conduct of the Anglo-North Irish Fish Producers Organisation (Anifpo) and local boat owners will examine concerns over the employment of overseas workers, according to the Seafood Ethics Action (Sea) Alliance, the business group overseeing the investigation…

Many overseas crew are employed through what is widely viewed as an immigration “loophole”, whereby if boats fish in international waters they are not considered to be in UK work despite operating out of UK ports on UK-registered vessels.

As part of an FT investigation into the so-called “transit visa” scheme last month, Filipino crew working on some Anifpo member boats said they had been subject to various forms of mistreatment…

Seven supermarkets and seafood business members of the Sea Alliance are funding the probe into their Northern Irish supply chains. The alliance, which includes Tesco, Asda, Morrisons and Whitby Seafoods, represents 95 per cent of the UK seafood market…